General :: FTP Download ---Procedure And Estimating Dynamic Space Required?

I have just downloaded Slack- 13.37 using Filezilla..I downloaded from an FTP server the entire directory of Slackware - Current (32 Bits) ..There were some problems encountered:1. When I selected the entire folder in FZ , the Queue size was reported as 4 GB.2. I started downloading and after significant time , still the Queue size was reported as around 3.8 GB..I was perplexed as I have a decent bandwidth and it cannot be. To dispel my doubt , I saw the properties of the Slackware directory in which it was downloading. It showed 1.9 GB.. Is the Q size not dynamic? (Total size - Downloaded size)

3. I was on the edge of my seat as my HDD had only roughly about 4 GB ...So , the Q size was kinda misleading..In a haste , I thought I would remove 2 big installations and wiped off Openoffice as anyway I was planning to go in for libre...I moved some other files to a different partition to ensure additional space4. At the end , early in the morning I woke up and saw it had finished ..But there was a failed transfer of 1 hidden file ..There is still 450 MB left in my partition, dont know why it got omitted.5. Now I want to check the integrity of the download bfor burning to a DVD..Should I use md5 sum? I am not able to determine slackware size by googling...In fact I should have gone in for a pre compiled ISO instead of this directory! But it wasnt available yesterday..6. Is there any good download manager like DAP/ Orbit / Leechget which also gives options like turning off comp after download (useful for overnight installs)...The DW helper in Mozilla is not that good ...I want a utility to split the download into 4/5 channels and speed up the download and most importantly show a graphical menu clearly showing Speed, Size, Time left , etc similar to windows DM